Japanese Patent Laying-Open No. 2003-209969 has disclosed a power supply control system provided with a plurality of power supply stages. This power supply control system includes a plurality of power supply stages that are connected in parallel together and supply a DC power to at least one inverter. Each power supply stage includes a battery and a boost/back-boost DC-DC converter.
In this power supply control system, the plurality of power supply stages are controlled such that a plurality of batteries included in each of the power supply stages are uniformly charged and discharged to maintain an output voltage for the inverter.
However, the above Japanese Patent Laying-Open No. 2003-209969 has merely disclosed that the plurality of power supply stages are connected in parallel and are operated to charge and discharge uniformly the plurality of batteries included in each of the power supply stages, and has not particularly discussed a method of controlling each power supply stage for suppressing a loss in the whole power supply control system.